Growth Factors & IGF

PEG-MGF

Also known as Pegylated MGF · Pegylated Mechano Growth Factor · IGF-1Ec · MGF

PreliminarySubcutaneous injectionIntramuscular injectionNot approved by the FDA for any indication; no IND or registered human clinical trials are publicly recorded as of 2026. It is distributed as a research chemical not subject to FDA quality oversight, and compounding-pharmacy availability is very limited. Prohibited in sport by WADA, which names mechano growth factors (MGFs) under class S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics) on the 2026 Prohibited List. Some jurisdictions (e.g., Australia, Canada) treat IGF-1 variants including MGF as prescription-only (Schedule 4) substances, making unauthorized import unlawful.

PEG-MGF is a polyethylene-glycol-conjugated form of Mechano Growth Factor (MGF), the C-terminal E-peptide of IGF-1Ec, a splice variant of the IGF-1 gene that muscle tissue expresses in response to mechanical loading or damage. In preclinical research the MGF E-peptide has been proposed to act on quiescent muscle satellite (stem) cells to promote their proliferation, reportedly through a pathway distinct from the classical IGF-1 receptor; however, findings are conflicting, and at least one peer-reviewed study reported the synthetic MGF peptide had no apparent effect on myoblasts or primary muscle stem cells. Native MGF is reported to survive only minutes in circulation, and the PEG moiety is intended to slow enzymatic degradation and extend its presence. The bulk of the published evidence comes from in vitro cell-culture and animal studies, with human data limited to mRNA-level responses to exercise rather than demonstrated clinical outcomes. A peer-reviewed minireview notes that critical evidence is lacking that an endogenous MGF E-peptide product is actually generated in vivo, and no human clinical efficacy trials have been reported. PEG-MGF is sold and handled as a research chemical and is not an approved drug.

Studied / used for

Investigated in preclinical models for activation and proliferation of muscle satellite (stem) cells, with conflicting findings across studies
Studied in animal models for potential roles in skeletal muscle repair and regeneration after injury
Investigated for possible effects on muscle hypertrophy following mechanical loading
Examined as an IGF-1 splice variant in tissue-repair signaling research

Commonly reported side effects

Injection-site reactions commonly reported, including pain, redness, and mild swelling
Temporary fatigue reported by some users
Joint stiffness or joint pain reported anecdotally
Reports of changes in fluid balance (swelling)
Lowered blood glucose reported anecdotally; human safety data are very limited

Preliminary. Mostly early or animal studies. This reflects the strength of the research base, not effectiveness or a recommendation.

Not medical advice.

This is an educational reference. Peptalk does not recommend, prescribe, endorse, or rate any compound, and provides no dosing information. Do not start, stop, or change any peptide, hormone, supplement, or therapy based on this page. All clinical decisions must be made with your licensed healthcare provider.

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